Exploring the effect of ion concentrations on the electrode activity and stability for direct alkaline seawater electrolysis

Studying the electrode activity and stability changes caused by the increasing ion concentration during the alkaline seawater electrolysis is crucial to exploit industrial-level seawater electrolyser. Herein, the concentration of hydroxide ion (OH−), chlorine ion (Cl−), and the other ions in alkaline seawater (OIAS) is investigated to understand the activity and stability for nickel foam (NF) electrodes as both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrodes. As a whole, the activity of HER electrode is mainly dropped with the increasing concentration of OH−, while the OER electrode is enhanced with the increasing concentration of OH− and Cl−. However, the all (OH−, Cl− and OIAS) increasing ion concentrations decrease the HER electrode stability, while the Cl− reduces, the OH− and OIAS enhances the stability of OER electrode. Moreover, the chloride evolution reaction (ClER) in 6 M NaOH with seawater can be ignored even though the concentration of salts in alkaline seawater reach to saturation.